The present invention is related to filter devices, more particularly, filter devices which are subject to high acceleration forces, such as will be encountered in the firing control of an artillery shell.
In the aforementioned application, the artillery shell will be accelerated for a very short period of time, such as a few miliseconds, to a very high speed. The acceleration period will last only during the time that the shell is in the propelling device, such as a cannon or gun. During this period of time, the acceleration forces on the shell will be extremely great, and will terminate when the shell leaves the propelling device.
Heretofore, the firing controls for such shells employed capacitors and coils which were encapsulated to provide a sufficiently rigid construction to resist the large acceleration forces imparted thereto. Although such former devices were of sufficiently rugged construction, to avoid damages when subjected to large acceleration forces, they have not been found to have satisfactory stability when subjected to temperature variations. In addition, other former devices employed quartz crystal which were configured for thickness mode vibrations to operate at very high frequencies, such as in the megahertz range, requiring a considerably large number of divider circuits to make them suitable for operation in the required frequency range for artillery shell firing controls. Therefore, it has been found desirable to provide a filter device which would be sufficiently rugged to resist damage when subjected to such large acceleration forces, but also would require less divider circuits, and thus result in less space and lower power requirements.